Despite the recent excitement about smartwatches it's not a new idea - the tech industry has been trying to come up with a viable watch-like computing device for decades. Here are some of the highlights.
Could you get more futuristic than an internet-enabled designer watch running an open source operating system?
Sadly 2001 got there first: IBM Research and Citizen Watch built a Linux-based watch called WatchPad, which they hoped would illustrate the viability of the then-novel operating system "across all platforms, from large enterprise servers, to medium-sized and small servers, workstations, desktop systems, laptops and the smallest intelligent devices".
The device featured a QVGA (320 x 240 pixel) LCD screen, Bluetooth and accelerometer - and ran on Linux version 2.4. It had a battery life of only a few hours.
"Internet-enabled watches are a popular publicity gimmick," said CNET at the time, and many would still agree today.
Still, the WatchPad wasn't the only smartwatch around - another early device of note was the Matsucom onHand PC, with a calendar-and-scheduling program, an address book, a notepad, an expense keeper, four games - and a joystick to navigate all of that.
The Fossil Wrist PDA came in Palm and Pocket PC version and with a 190KB memory that could store 1,100 contacts, 5,000 To Do items, 800 appointments, or 350 memos.
The 2002 device aimed to prove that a watch could deliver all the capabilities of a PDA (remember them?) into a piece of hardware that could be worn on the wrist. This was one of number of smartwatch models released by Fossil during this period.
Inevitably Microsoft had its own smartwatch project running, as part of its Smart Personal Objects Technology (Spot) Initiative.
As a Microsoft exec said at the time: "Imagine how handy it would be to have a travel alarm clock that, in addition to telling time very accurately and auto-adjusting to time-zones, could also wake you to your favorite WMA-encoded music, display information about road closures along your expected travel route, and deliver urgent messages." Yup, very handy.
This information was delivered via FM radio signals which could be picked up in around 100 US cities (plus some in Canada), through an antenna built into the watchstrap. The watch above came with a free year of MSN Direct Smart Plan which delivered news, business, technology and sports reports to the watch. For an extra $20 users could also get access to two days' worth of Outlook Calendar appointments and text messages via MSN Messenger.
The watches - perhaps unsuprisingly - weren't a huge success. As well as being bulky and requiring frequent charging, the small screen meant a limited amount of information could be delivered and the ongoing cost of subscribing to services made them a less than appealing prospect. Microsoft shuttered its Spot project in 2008.
Still, the demise of Spot did little to dampen the tech industry's enthusiasm for smartwatches. But, as mobile phones become more sophisticated, the idea of pairing a watch with a phone became something for tech companies to explore.
Here's the Sony Ericsson MBW-150 - the watch could be paired with a Sony Ericcson phone via Bluetooth and had a small single line OLED display. When an incoming call is received, the watch would vibrate and show either the name of the caller or their number. The watch could also notify the wearer about new text messages, and came in three models: classic, music (above) and executive.
This is one of the slightly more unusual smart devices - a watch that was also a phone. This Samsung S9110 from 2009 was at the time touted as the world's thinnest watchphone, sporting a 1.76-inch touchscreen, Bluetooth, email support and MP3 playback. Samsung is another company that has made a number of attempts to crack the smartwatch market - more of which later in this gallery.
The 12mm thick device also supported voice recognition and speakerphone and had a 40MB internal memory. Smartwatches that make calls are now enjoying something of a breakthrough with new LTE-enabled devices.
Of course, if you want an Apple iOS watch, it has long existed in the shape of the iPod nano.
Simply adding a wristband (the above strap is from Hex) turned the mini music player into a watch, too.
The WIMM watch running a modified version of Android was actually a styled as a developer kit device rather than a consumer device, with the aim of kickstarting an app ecosystem based around the device.
The Wimm was well-received but short-lived: during the summer of 2012, WIMM Labs entered into an "exclusive, confidential relationship" for its technology and ceased sales of the developer preview kit (Google later confirmed that it had snapped up the company).
This is one of Sony's watch-like devices from 2012, the Sony Smartwatch, which effectively functions as a second screen for your Android phone, which allowed you to read email, SMS and other notifications such as Twitter.
The Pebble watch began life as a Kickstarter project aiming to raise $100,000. It raised $10.3m instead.
The watch is compatible with iPhones and Android devices running OS 2.3 and up, but not Blackberry or Windows Phone 7. Alerts include incoming call, SMS, iMessage, calendar, Facebook messages and Twitter.
The rather brilliantly-named Martian Watches offers the Passport watch which features voice controls so that it can function as a speakerphone your smartphone or allow you to access services such as Siri.
The arrival of Google's Android Wear, which aims to make smartwatches operate better with Android smartphones, has reinvigorated the smartwatch market, with a number of consumer electronics manufacturers having another go.
Because smartwatches have tiny screens and batteries, Android Wear rethinks the Android user interface and stripped it back to conserve power -- and stop smartwatches driving users crazy with constant updates. It builds on the notification system used by Android apps, giving devices a 'context stream' made up of a vertically-scrolling list of 'cards' carrying small pieces of information.
Above is Motorola's Moto 360 device.
Here's Sony's Smartwatch 3 which, like the Moto 360 runs Android Wear.
It features built-in microphone, accelerometer, compass, gyro and GPS sensor technology which means it is useful without a smartwatch - for example the watch also has 4GB local memory which means you can sync playlists, connect a Bluetooth headset and go for a run leaving the smartphone at home.
This is the LG G Watch R. Anothe Android Wear device it's powered by a 1.2GHz Snapdragon 400 processor and features 4GB of storage, 512MB of RAM and a 410mAh battery.
It features a gyroscope, accelerometer, compass, barometer and heart rate monitor under its 1.3-inch round screen.
Samsung has been making a major push when it comes to smartwatches such as the Gear S, seen above. The Gear S is notably in that it will allow you to make calls rather than just act as a second screen for a smartphone.
Adrian Kingsley-Hughes notes elsewhere on ZDNet that the Galaxy Gear S is about as powerful as the first-generation iPhone that Apple released back in June 2007, but on your wrist, reflecting how much components have shrunk in size over seven years.
Of course while all the attention is on the smartwatches, it is the fitness bands that are selling: how these two markets evolve and emerge over the next year or two will be interesting. Here's Garmin's Vivosmart which combines some of the elements of a smartwatch with the standard fitness band offerings. The device tracks fitness but also allows wearers to check calls, texts, emails and meetings on a 'hidden' OLED touchscreen which is displayed with a double tap.
Pebble's 2015 Pebble Time Steel had a professional design and longer battery life.
The Pebble Time Steel has a CNC-finished 316L stainless steel casing, included leather and stainless steel straps, increased battery life of 10 days (Pebble Time has a 7-day rating), and three finish options.
Read on for more about this Apple Watch competitor in our full story.
This is likely to be the defining product in the smartwatch category for some time to come. The first version of the Apple Watch launched in April 2015 to some good reviews and rapidly took on a dominant position in the market; it now accounts for about half of smartwatch sales and more than three-quarters of the revenue according to analysts.
Fossil was an early player in smartwatches and in 2015 came back with a new range which had a rather different look-and-feel to its earlier devices, featuring a touchscreen display, wireless charging and running Android Wear. Since then it has extended its range of smartwatches significantly.
This is Huawei's first smartwatch, a circular Android Wear-powered device.
Compatible with smartphones running Android 4.3 or higher, the device features a 1.4-inch Amoled display with a resolution of 400 by 400 pixels resolution (286ppi). It also includes a heart rate monitor sensor, a six-axis motion sensor, and a barometer.
Read on for our full story about the Huawei Watch.
LG Electronics' smartwatch, the LG Watch Urbane debuted at the Mobile World Congress in Barcelona, Spain in 2015.
Like the preceding LG G Watch R, it has a round screen and metal body and uses leather straps in a design that the South Korean tech giant called "classic circular, like a real watch".
Since the arrival of the Apple Watch competition has increased again, with one new feature the addition of LTE connectivity which enables watches like the Samsung Gear S3 Classic seen here operate independently of a smartphone.
Huawei's Watch 2 has similar LTE functionality.
Apple's Watch Series 3 is the latest to add LTE functionality to one of its models.